Fabrics used as forming fabrics, dryer felts, conveyor belts on pulp filtration drums, and industrial fabrics in general are of a great variety, examples of which are the typically woven fabrics and the needled fabrics having a woven base. Additionally, there are certain fabrics which are needled without a woven base and others of differing construction but of nonwoven form. These fabrics are generally used in the form of a conveyor or endless belt. The fabric therefore must be of endless configuration. Some fabrics are actually constructed endless, for example, by weaving in tubular form, whereas others are constructed in rectangular form and their free ends joined together to form the endless belt or tube. It is to this latter type of fabric that this invention is directed.
Various methods of joining fabric ends to form an endless belt have been utilized through the years in the industrial fabric industry. In recent years, however, the treating of fabrics and the materials available from which fabrics are formed, such as the synthetic materials, have resulted in fabrics which are very strong and durable and which have many improved characteristics in comparison to such as were used in the recent past. The machines upon which these fabrics are run today are operated at much higher speeds than heretofore, thereby requiring that they be of great durability.
Through the application of the new synthetic materials and through the utilization of various treatments and finishing procedures the fabrics used today can be operated and used over longer periods than previously even though in today's machinery they are subjected to processes which have a greater tendency to deteriorate and damage the fabrics.
The traditional method for making fabrics such as papermaker dryer felts endless is the insertion of metal hooks in the ends to be joined. The procedure involves a machine that forces the points of the metal hooks into the fabric or into a webbing that is later sewn to the fabric. These hooks are inserted across the width of the fabric. This requires special equipment and the time needed is quite extensive. The resulting metal seam is inflexible and subject to abrasion. If tension during use of the fabric exceeds the crimp force the metal hook can be pulled from the fabric.
The art has reached a degree of development such that the seams or joining areas of the fabrics whereat ends are joined to make them endless has become a weak part in the fabric. Improvements of fabrics through the use of chemical treatments and synthetic materials to increase life are of no use if the seams are not durable and able to withstand deteriorating forces. It is also not useful to have seams at seam areas which must be strengthened and treated so that the characteristics in these zones are totally different than the characteristics of the remaining portion of the fabric.